The invention relates to a focus adjusting device which uses an electric motor for adjusting the focus of the photographing lens of a camera.
In a camera which uses an electric motor to automatically adjust the focus, in response to a control signal provided by an automatic focus detector, the automatic adjustment cannot always satisfactorily focus the lens on the object because of the nature of the object. As a result, an auxiliary manually operated focusing means is often used in combination with the automatic focusing means. The auxiliary focusing means uses a method in which the distance ring is manually turned, or a method in which a switch is manually operated to suitably rotate the motor. However, the former method is disadvantageous in that performing the manual focusing operation after the automatic focusing operation is rather troublesome, and the latter method is disadvantageous in that it is difficult to provide a proper timing instruction to a high speed motor and if the motor is run at low speed it takes a relatively long time to set the lens at the focusing position. Furthermore, another method has been proposed in which the motor speed is changed between high and low speeds by operating a switch in two steps. However, this method is also disadvantageous in that the high speed cannot be smoothly switched over to the low speed.